This invention relates to universal joints for providing a rotational driving connection between two rotatable shafts, while allowing such shafts to be oriented at an angle relative to one another. More particularly, this invention relates to a constant velocity type of universal joint having an improved sealing structure that avoids the use of a flexible boot.
A universal joint is a well known mechanical coupling device that provides a rotational driving connection between two rotatable shafts, while permitting such shafts to be oriented at an angle relative to one another. Universal joints are commonly used in the drive train systems of vehicles. For example, universal joints are often used to rotatably connect a driveshaft tube between an output shaft of an engine/transmission assembly or other source of rotational power and an input shaft of an axle assembly including a pair of driven wheels. In such a vehicular drive train assembly, the rotational axes of the output shaft of the engine/transmission assembly, the driveshaft tube, and the input shaft of the axle assembly are rarely co-axially aligned. To accommodate this, a first universal joint is connected between the output shaft of the engine/transmission assembly and a first end of the driveshaft tube, while a second universal joint is connected between a second end of the driveshaft tube and the input shaft of the axle assembly. Universal joints are also commonly used to provide a rotational driving connection between the axle shafts and the driven wheels of the axle assembly.
Universal joints are commonly classified by their operating characteristics. One important operating characteristic relates to the relative angular velocities of the two shafts connected thereby. In a constant velocity type of universal joint, the instantaneous angular velocities of the two shafts are always equal, regardless of the relative angular orientation between the two shafts. In a non-constant velocity type of universal joint, the instantaneous angular velocities of the two shafts vary with the angular orientation (although the average angular velocities for a complete rotation are equal).
A typical constant velocity universal joint includes a cylindrical inner race that is connected to one of the shafts and a hollow cylindrical outer race that is connected to the other of the shafts. The outer surface of the inner race and the inner surface of the outer race have respective pluralities of grooves formed therein. Each groove formed in the outer surface of the inner race is associated with a corresponding groove formed in the inner surface of the outer race. A ball is disposed in each of the associate pairs of grooves. The balls provide a driving connection between the inner and outer races. An annular cage is typically provided between the inner and outer races for retaining the balls in the grooves. The cage is provided with a plurality of circumferentially spaced openings for this purpose.
As is well known, the above-described components of the constant velocity universal joint are usually disposed within a protective enclosure to prevent dirt, water, and other contaminants from interfering with the operation thereof. Typically, this protective enclosure has been embodied as a boot formed from a flexible material, such as rubber or other elastomeric material. The flexible material accommodates articulation or relative angular movement between the shafts connected to the inner and outer races of the joint, while maintaining a seal therebetween. Flexible boots of this general type are well known in the art for performing this function and have been found to perform satisfactorily in a variety of constant velocity universal joint structures at a reasonable cost for many years.
However, several drawbacks have been noted with respect to the use of conventional flexible boots in constant velocity universal joints. For example, flexible boots are relatively soft and, therefore, subject to puncture when impacted by stones or other objects encountered during operation of the vehicle. Flexible boots are also subject to degradation resulting from repeated flexing and exposure to chemicals and the elements during use. Also, flexible boots having a conventional convoluted configuration generally require a relatively large volume of lubricant to properly lubricate the constant velocity universal joint contained therein. All of these factors tend to limit the useful lifespan of the flexible boot. Thus, it would be desirable to provide a constant velocity universal joint having an improved sealing structure that avoids the use of a conventional flexible boot.
This invention relates to a constant velocity type of universal joint having an improved sealing structure that avoids the use of a flexible boot. The constant velocity joint includes a hollow outer joint member, an inner joint member disposed within the outer joint member, and a plurality of ball bearings extending into associated grooves formed in the inner and outer joint members to provide a rotational driving connection therebetween. A sealing assembly is provided for protectively enclosing the components of the joint. The sealing assembly includes an outer sealing member that is sealingly connected to the outer joint member. An outer surface of an inner sealing member is slidably and sealingly engaged with an inner surface of the outer sealing member. An annular flange provided on the inner sealing member slidably and sealingly engages an outer surface of an annular element. An inner surface of the annular element slidably and sealingly engages a shaft connected to the inner joint member. The outer sealing member, the inner sealing member, and the annular element cooperate to form a protective enclosure for the various components of the joint. A biasing element can be provided to positively urge the inner sealing element into sealing engagement with the outer sealing element. The protective enclosure is effective to prevent dirt, water, and other contaminants from contacting the various components of the joint, and to retain lubricant therein for such components.